The Syrian foreign ministry said on Tuesday that the United States informed Damascus' envoy to the United Nations before launching airstrikes against the Islamic State group in Syria.

The ministry issued a brief statement, carried by Syrian state media, saying that "the American side informed Syria's permanent envoy to the U.N. that strikes will be launched against the Daesh terrorist organization in Raqqa."

The statement used an Arabic name referring to the Islamic State group, which seized large chunks of Syrian and Iraqi territory in a blitz this summer.

The airstrikes hit targets in and around the Syrian city of Raqqa and the province with the same name, activists said, adding that there were casualties among Islamic State militants on the ground. The city of Raqqa is the militant group's self-declared capital in Syria.

The ministry statement was Damascus' first official reaction after the U.S. and five Arab countries launched airstrikes on Islamic State group's targets in Syria late on Monday, expanding a military campaign into a country whose three-year civil war has given the brutal militant group a safe haven.

U.S. officials said the airstrikes began around 8:30 p.m. EDT (0030 GMT), and were conducted by the U.S., Bahrain, Qatar, Saudi Arabia, Jordan and the United Arab Emirates.

In the past, Syrian officials have insisted that any strikes against the Islamic State group in the country should come only after coordination with Damascus. Without their consent, Syrian officials have said such airstrikes would be an act of aggression against Syria and a breach of the country's sovereignty.

However, U.S. officials have ruled out direct coordination with Syrian President Bashar Assad's government.

Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, an activist group, said the airstrikes targeted the northern province of Raqqa, as well as its provincial capital.

The Observatory, which has a network of activists around the country, said the attacks came after drones flew over areas under control of the Islamic State group.

Abdurrahman said about 20 air strikes hit Raqqa province, adding there were casualties among jihadi fighters, mostly on checkpoints. He said that in addition to the city of Raqqa, there were strikes on the towns of Tabqa, Ein Issa and the border town of Tel Abyad on the border with Turkey.

An anti-militant media collective entitled "Raqqa is being silently slaughtered" said that the targets included the governorate building or municipality used by Islamic State militants as their headquarters, and the Brigade 93, a Syrian army base that the militants recently seized.

Other airstrikes targeted a military air base recently captured by jihadi fighters in the town of Tabqa as well as the town of Tel Abyad on the border with Turkey.